FDA Approves Regeneron's Pasatru, First Treatment to Reduce FOP Flare-Ups and Lesions

FDA Approves Regeneron's Pasatru, First Treatment to Reduce FOP Flare-Ups and Lesions

On August 19, 2026, the U.S. Food and Drug Administration (FDA) approved Regeneron Pharmaceuticals' Pasatru (garetosmab-grts) to reduce the formation of new abnormal bone growth outside the skeleton—known as heterotopic ossification (HO) lesions—and clinician-assessed flare-ups in adults with fibrodysplasia ossificans progressiva (FOP). Pasatru is a fully human monoclonal antibody that blocks Activin A, a protein identified by Regeneron scientists as critical to the development of HO lesions.

Efficacy in the Phase 3 OPTIMA Trial

The FDA approval is based on results from the Phase 3 OPTIMA trial, which evaluated 63 participants aged 18 and older with active FOP. The trial demonstrated a dramatic reduction in new bone lesions at 56 weeks:

"At 56 weeks, both doses of Pasatru, 10 mg/kg (n=23) and 3 mg/kg (n=19), met the primary endpoint and were highly efficacious in reducing the total number of new HO lesions as compared to placebo (n=21), demonstrating a 90% (2 lesions vs. 19 lesions) and 94% (1 lesion vs. 19 lesions) reduction, respectively, as assessed by computed tomography (CT) scan."

Furthermore, Pasatru demonstrated a significant reduction in clinician-assessed flare-ups, a key secondary endpoint:

"The number of clinician-assessed flare-ups during this time, a key secondary endpoint, were 9 for Pasatru 10 mg/kg (88% reduction compared to placebo), 53 for Pasatru 3 mg/kg (15% reduction compared to placebo), and 66 for placebo."

Administration, Pricing, and Safety

• Dosing & Setting: The recommended starting dosage is weight-based at 10 mg/kg administered intravenously once monthly (every four weeks). It can be decreased to 3 mg/kg if not tolerated. The therapy can be administered across a range of care settings, including home infusion where appropriate.
• Pricing: According to industry reports, the annual list price ranges from $693,000 to $2.1 million based on patient weight.
• Safety: Common adverse reactions (occurring in $\ge 10%$ of patients) include abscess, acne, increased hair growth, madarosis (loss of eyebrows), oral ulcers, epistaxis (nosebleeds), folliculitis, paronychia (nail infection), and rash.

George D. Yancopoulos, M.D., Ph.D., co-founder and Chief Scientific Officer at Regeneron, remarked on the decade-long scientific journey:

"The approval of Pasatru is the culmination of decades of pioneering research that Regeneron has pursued alongside the FOP community, rooted in our discovery of the role that Activin A plays in driving this disease. People living with FOP have needed a new treatment option for this devastating condition far too long¹, much like many others living with a rare disease."